Feature: Pinned notifications excluded from Snooze All

[cursor]

Description

Add the ability to "pin" event notifications so they are excluded from batch snooze operations (Snooze All, Snooze All Collapsed).

Use Case

When managing many reminders, users often use "Snooze All" to quickly push everything back. However, certain critical events should not be accidentally snoozed this way - they need to stay visible and active.

Examples:

• A flight check-in reminder you must not miss
• A medication reminder
• An important meeting happening very soon

Proposed Behavior

1. Add a "pin" action to event notifications (long-press menu or dedicated button)
2. Pinned events display a visual indicator (pin icon)
3. Pinned events are excluded from:
   • Snooze All
   • Snooze All Collapsed
   • Potentially: Dismiss All (configurable?)
4. Pinned events can still be individually snoozed/dismissed
5. Pin state persists until manually unpinned or event is dismissed

Implementation Notes

• Could add a isPinned flag to EventAlertRecord
• Modify snoozeAllEvents() and snoozeAllCollapsedEvents() to filter out pinned events
• Add pin/unpin toggle to ViewEventActivity and notification actions
• Visual indicator in event list and notification

Related

• Feature: Multi-select events for batch snooze operations #182 - Multi-select batch snooze (pinned events could also be excluded from multi-select by default)
• Feature: Extended hashtag system for per-event behavior control aka per event pills #185 - Extended hashtag system (could potentially use #pin hashtag as an alternative mechanism)

[williscool]

this will be a good filter pill too! make sure its done along with it

refs #92 refs #185